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Throughout the Green River system, including the Little Snake River, the response of a given alluvial reach to water management is constrained by the geologic controls of canyon reaches. The Little Snake, Yampa and Green rivers are a blend of alluvial reaches and bedrock controlled reaches. The bedrock controlled reaches (of which there are several in the lower Little Snake basin) are confined by outcrops or have bedrock exposed at the river level which establishes the average stream gradient. The Little Snake River enters a narrow bedrock canyon at the Lily Gage and upstream of the gage the river channel is a wide, rather shallow sand-bed stream. The gradient of the sand-bed reach is partly controlled by the canyon entrance base elevation and therefore, this relatively short sand-bed reach has a limited range of potential slope and channel geometry adjustment to changes in upstream sediment supply. Uttle Snake River Flows and Channel Morphology The Little Snake River has a wide range of discharges and sediment loads typical of tributaries to the Colorado River. Peak flows have ranged from a low of 934 cfs (26 m3/s) in 1934 to 16,700 cfs (473 m3/s) in 1984 with a mean annual peak of 5,420 cfs (153 m3/s) for the period of record 1923 to 1994. The mean annual sediment load varies from 440,000 tons to in excess of 3,000,000 tons. The Little Snake River is capable of delivering huge quantities of sediment in a relatively short period. In 1962, the sediment load during a four day period was 1,156,000 tons (O'Brien 1984). The alluvial reach (Reach IV) of the Little Snake River extends approximately 65 km upstream from the Lily Gage. This is a predominately sand-bed reach which meanders through pasture and cropland valley bottomland and at low flow is a wide, anastomosing sand-bar channel. Large macroform bars appear which shift back and forth across the channel. Cottonwood and tamarisk seedlings grow in vast numbers on the exposed sand bars. During high flows the channel is 24